The root is the only optional note in an augmented seventh chord, the fifth being required because it is raised.[4] This alteration is useful in the major mode because the raised 5th creates a leading tone to the 3rd of the tonic triad.[2] See also dominant.

In rock parlance, the term Augmented seventh chord is sometimes confusingly and erroneously used to refer to the so-called "Hendrix chord", a 7♯9 chord which contains the interval of an augmented ninth but not an augmented fifth.[5]